Baleen Whales Visit Our Waters On Journeys

Nature Notes

December 29, 2002|By BETSY WOLIN Guest Columnist

Cries of shorebirds, calls of songbirds, honking of Canada geese ... the noisy parade of migrating birds passes through Hampton Roads each fall. And each fall, a silent migration passes by in our coastal waters. The largest creatures on Earth, the baleen whales, are migrating off the coast of Virginia without most of us ever knowing it.

Many different species of animals migrate, or move between different locations, on a seasonal basis. Food is the main reason that most animals migrate. Warblers that spend the spring breeding season in Virginia gorging on our abundant insects may travel as far south as Peru and Columbia to find a supply of their favorite insect foods in wintertime. But the reason for the vast distances traveled each year by the baleen whales may be more complex.

Baleen whales get their name because their mouths contain many large plates called baleen that strain out tiny plankton and small fish as they move through the water. The largest mammals on Earth therefore feed on some of the smallest animals in the ocean.

Many species of baleen whales spend their summers in the cold, nutrient-rich waters of the Arctic where the supply of plankton is abundant. In the fall, they start to move southward toward warmer, subtropical waters. Calves are born and mating often occurs in these warm waters during the winter months. For gray whales and humpback whales, these migrations may stretch more than 5,000 miles each way, the longest seasonal movements of any mammal. Once on these wintering grounds, many baleen whales do not consume any food during the breeding season.

If food is not a major reason why these giant animals migrate southward, what is? The movement to subtropical waters may instead provide a thermodynamic advantage. Once in these warmer waters, whales may need to devote less energy to keeping warm and therefore have more energy available for breeding, calving and nourishing their babies. Research into this and other intriguing aspects of whale migration is being conducted by biologists throughout the world's oceans.

Such research may prove critical for at least one species of baleen whale that passes by the Virginia coast each fall. The northern right whale was considered by 19th-century whalers as the "right" whale to kill: it had large amounts of blubber, it was slow and easy to catch, and it floated when killed. Originally the North Atlantic was home to an estimated 20,000 right whales. Today, less than 350 remain. With such a tiny population, the northern right whale is one of the most endangered mammals in the world.

Scientists have been studying the migration patterns of right whales for more than 20 years. To track whales, researchers first learn to identify and recognize individuals by their unique patterns of thickened skin patches (called callosities) around their heads. By logging the locations of individuals, a general migration route for right whales has been outlined.

Many right whales spend the spring in the food-rich waters off Cape Cod. In the summer, most of them congregate in waters within and near the Bay of Fundy off Canada. When autumn arrives, pregnant females migrate south along the East Coast to their calving grounds off the coast of Georgia and Florida. Calves are born there in December and the nursing pairs travel back to the Cape Cod area in the early spring.

Although females make the journey south, it is not known where males and juveniles go in the winter. Researchers hope to use implanted satellite transmitters to solve these mysteries of right whales and their migration. Perhaps the new information will help scientists to better protect these whales from extinction.

As fall turns to winter, the silent migration of right whales and other baleen whales past Hampton Roads will dwindle. But just as migrating flocks of birds will pass through our area this spring, these quiet giants of the sea, many with their new calves in tow, will travel through our waters once again.